The last thing anyone wants to worry about on a cold winters night is whether or not the air coming out of their vents is warm enough.
That being said, what temperature is warm enough?
With over a decade of field experience I have checked and adjusted air temperature on all types of heating equipment and I’m here to tell you what to look for and when to be concerned.
What Temperature Should Air Be Coming Out of Vent When Heating?
The answer actually varies greatly depending on several different factors, but typically ranges anywhere from 85-125 degrees when heating.
Although this temperature is important, it’s even more essential to find the temperature rise of the heating system. The temperature rise is the difference between the supply air (air coming out of the vents) and the return air (air going into the vents). How hot should air be coming out of the vents will depend on your temperature rise.
Different equipment types and climates typically have different temperature rises, but this number can tell us a lot about how the equipment is operating.
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Heat Pump Vent Temperature
A very popular heating source is the electric heat pump.
Of all equipment types, the heat pump has the lowest supply air temperature and temperature rise. Depending on indoor and outdoor temperatures, the heat pump discharge air temperature should range between 85-100 degrees.
Heat pumps don’t create heat, they move heat energy from the outside air to the inside air which allows them to be very efficient, but the actual air temperature is typically lower than that of a fossil fuel furnace.
Keep in mind our body temperature is around 98 degrees, so the heat pump air temperature at the register may not feel very warm, but it’s enough to keep the house at a comfortable temperature.
The outdoor temperature contributes to the amount of heat coming out of the vents greatly. Because the heat pump is moving heat energy from the outside air, the lower the outside air temperature, the less heat can be exchanged.
In colder climates, a backup heat source is required to maintain indoor comfort. Typically electric heat vent temperature is about the same as the heat pump, sometimes a few degrees higher.
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Gas and Oil Furnace Vent Temperature
As a licensed HVAC contractor, a common question I receive is — how hot should the air from my furnace be?
Gas and oil fired furnaces have a higher supply air temperature than heat pumps do, usually 110-125 degrees and on older models even up to 150 degrees. These temperatures easily warm a house, but if they’re too high they can actually cause the house to feel uncomfortable and be inefficient.
Gas furnaces typically have a temperature rise of 40-70 degrees and the rating plate on the equipment should list this. In my experience, I typically aim for the 40-50 degree temperature rise.
How To Check Temperature of Air Coming Out of Vents?
You can use a digital thermometer to measure the supply and return air from your vents.
Place the thermometer in the vent after the furnace kicks on and leave it there for about 10 minutes. Write the number down so you don’t forget it and do the same thing in the return vent.
After another 5 minutes or so, record that number and do the math. Subtract the return temperature from the supply temperature and that will give you your temperature rise.
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Factors That Affect Air Temperature
While there are many variables that can change the temperature of the air coming out of the vents, one of the biggest is airflow.
High Temperature From Vents
Dirty or clogged filters prevent enough air from moving across the heat exchanger and will cause the temperature to rise significantly.
Most of the time this will trip the high limit switch or other safeties used for high temperatures. Replacing your filter on a regular basis will prevent this from being a problem.
Poorly Sized HVAC Ducting
Improperly sized duct or equipment is another reason you may have a temperature issue.
Undersized ducts will act similarly to a clogged filter, high temperatures and limit trips. Oversized equipment will do the same. If your furnace and ductwork is not properly sized, you will always have temperature related issues with your equipment and your house won’t be as comfortable as it should be.
Low Temperature From Vents
Most of the time low temperature indicates a heating problem and will most likely need to be diagnosed by a qualified technician.
If it’s a heat pump, it could be low on charge or have dirty coils. If it’s a gas furnace, it could be any number of problems. Both systems have multiple components that can fail and will need to be properly diagnosed to identify what steps to take.
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Vent Temperature For Comfort
If the temperature coming from your vents is too high or too low, there’s a good chance you’ll be uncomfortable.
Temperature Too Low
If the temp of air coming out of your vents is too low, your house may not come up to temperature.
Your furnace or heat pump will run continuously causing high utility bills and never feeling comfortable. This may not be something you notice with milder outdoor temperatures, but as soon as the temperature gets cold your house will too.
Temperature Too High
High vent temps can cause something called stratification.
If the air is too hot, it will rise too quickly and stay at the ceiling, leaving colder temperatures at the floor. When this happens, most people complain that their feet are cold even though the thermostat is satisfied and the house is warm.
Uneven Temperatures
Another issue is uneven temperatures throughout the house. Without balanced airflow and balanced temperature some rooms may be hotter or colder.
Having the right temperature allows the system to circulate air and heat evenly and keep the all the rooms comfortable. Adjusting airflow and balancing vent dampers can help keep all rooms evenly heated.
Ensuring you have the proper temperature rise will contribute greatly to keeping everyone comfortable all winter long.
Vent Temperature For Efficiency
If your vent temperature isn’t within range it can be significantly less efficient.
If your system is running extremely long run cycles because of low temperature, it loses all its efficiency and becomes quite costly to operate. If its running short cycles because of high temperatures, the house will have hot and cold spots and the wear and tear on your equipment increases.
If your house is uncomfortable, you may turn your thermostat up trying to compensate, which will raise the cost of your utility bills. Making sure your temperature is within range will help you achieve the highest energy efficiency your equipment can offer.
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Frequently Asked Questions
What should I do if the temperature of air coming out of my heating vents is too low/high?
If the air coming out of your heating vents is too high or low, start by checking your air filter and making sure your vents are fully open. If the temperature doesn’t seem to change, it’s best to call a professional to properly diagnose the issue and give you some options.
How can I measure the temperature of air coming out of my heating vents?
Measuring the temperature coming out of your heating vents is relatively easy. Place a digital thermometer or infrared thermometer in the vent while the system is heating to accurately record what the air temperature is.
What are some common reasons for low/high temperatures of air coming out of heating vents?
Common reasons for low or high temperatures coming out of your vents are usually airflow related. Dirty filters and dirty evaporator coils will prevent proper airflow. Incorrect blower speed and duct related issues can also affect vent temperature. More significant issues related to the operation of the equipment are possible as well, but would need to be properly diagnosed.
How often should I check the temperature of air coming out of my heating vents?
You should check the temperature coming out of your vents whenever you feel there may be an issue. I check air temperature on every service call I go on. It’s quick and easy to do and can help identify potential issues you may have down the road.
Can the temperature of air coming out of heating vents affect my energy bill?
The air temperature coming out of your vents can definitely affect your energy bill. Whether it’s too low or too high, both ways will be less efficient and cause an increase in your bills.
Can the temperature of air coming out of heating vents affect the lifespan of my heating system?
The temperature of the air coming out of your vents can help identify significant issues that will reduce the lifespan of your equipment. Any time your equipment is working harder than it needs to will reduce life expectancy. Too much heat on your heat exchanger with constant limit trips almost always cuts the lifespan of that heating system in half.
How can I improve the temperature control in my home?
To improve the temperature control in your home, regularly change your air filter and have regular maintenance performed. Many issues can be caught and taken care of before they become significant problems.
Conclusion
Knowing what your temperature rise is and how warm the air from your heating vents should be can help you be energy efficient and keep your house comfortable.
It’s also important because it can indicate a potential issue that can be corrected and keep you from going without or spending tons of money on repairs. Checking your vent temp is an easy thing to do, and you may even have a digital thermometer already in your kitchen. It’s an easy thing to do to ensure your heating system is operating correctly.
Thanks for reading, I hope this helps!